TW201513387A - Processing method for optical device wafer - Google Patents

Abstract

The subject of the present invention is to provide a laser processing method capable of efficiently superposing a light-emitting layer onto the surface of a single-crystal substrate, dividing an optical device wafer into a plurality of optical devices along the predetermined cutting lines, in which the optical devices are formed inside a plurality of regions of the optical device wafer defined by the predetermined cutting lines of a grid shape, and preventing the quality of the optical devices from downgrading. The solution means is a wafer processing method cutting an optical device wafer into a plurality of optical devices along the predetermined grid-like cutting lines in which the optical device wafer is formed by superposing a light-emitting layer onto the surface of a single-crystal substrate and forming the said optical devices such as light-emitting diodes, laser diodes, etc. inside a plurality of regions defined by the predetermined cutting lines of the grid shape. This method includes: setting the numerical aperture (NA) of a condensing lens such that the numerical aperture (NA) of the condensing lens collecting the pulse laser light divided by the refractive index (N) of the single crystal substrate is in the range between 0.05-0.2; positioning the focus point of the pulse laser light at the vicinity of the light-emitting layer from the backside of the single crystal substrate and carrying out irradiation along the predetermined cutting lines; after executing a light-emitting layer removal step for removing the light-emitting layer along the predetermined cutting lines, positioning the focus point of the pulse laser light at the vicinity of the surface of the single crystal substrate from the backside of the single crystal substrate of the optical device wafer and executing radiation along the predetermined cutting line; and a step of forming shielding through-holes to form the shielding through-holes by the amorphous growth of narrow holes and the protection thereof from the surface of the single crystal substrate to its backside.

Description

Optical device wafer processing method Field of invention

The present invention relates to a plurality of light-emitting layers formed on a surface layer of a single crystal substrate such as a sapphire (Al ₂ O ₃ ) substrate or a tantalum carbide (SiC) substrate, and is divided by a plurality of predetermined dividing lines formed in a lattice shape. In the region, an optical device wafer in which an optical device such as a light-emitting diode or a laser diode is formed, and a method of processing the optical device wafer into a single optical device along a predetermined dividing line is formed.

Background of the invention

In the optical device manufacturing program, the light-emitting layer is formed of an n-type nitride semiconductor layer and a p-type nitride semiconductor layer on a surface layer of a single crystal substrate such as a sapphire (Al ₂ O ₃ ) substrate or a tantalum carbide (SiC) substrate. An optical device wafer is formed by forming an optical device such as a light-emitting diode or a laser diode in a plurality of regions defined by a plurality of predetermined dividing lines formed in a lattice shape. Further, by cutting the optical device wafer along the dividing line, the region in which the optical device is formed can be divided to manufacture individual wafers.

As a method of dividing the above-mentioned optical device wafer, there are also attempts to use pulsed laser light having a wavelength that is transparent to the wafer, and to align the concentrated light spot with the inside of the divided region to irradiate the laser light of the pulsed laser light. method. The segmentation method using this laser processing method is by using a wafer from The side of the side of the side converges the condensed spot inside to illuminate the pulsed laser beam having a wavelength that is transparent to the wafer, continuously forms a modified layer on the inside of the workpiece along the dividing line, and is formed along the surface This technique of modifying the layer and reducing the strength of the scribe line to apply an external force to divide the wafer (see, for example, Patent Document 1).

Further, as a method of dividing the optical device wafer along the predetermined dividing line, ablation processing is performed by irradiating a pulsed laser beam having a wavelength that is absorptive to the wafer along a predetermined dividing line to form a laser processing groove. In addition, an external force is applied to the predetermined dividing line in which the laser processing groove is formed to form the breaking starting point, and the technique for cutting is applied (see, for example, Patent Document 2).

Prior technical literature Patent literature

Patent Document 1: Japanese Patent No. 3408805

Patent Document 2: Japanese Patent Laid-Open No. Hei 10-305420

Summary of invention

However, since the condensed spot of the laser light is to be positioned inside the wafer to form the modified layer, it is necessary to use a condensing lens having a number of openings (NA) of about 0.8, in order to divide, for example, a wafer having a thickness of 300 μm into The individual devices must be repeated over and over again to form a majority of the modified layers, which has the problem of poor productivity.

Further, after irradiating the pulsed laser light having a wavelength that is absorptive to the wafer, Since the ablation process is performed near the irradiation surface of the wafer, and the energy does not penetrate into the inside of the wafer, in addition to the necessity of irradiating a plurality of pulsed laser rays along the dividing line to cause deterioration in productivity, there is also debris scattering. The problem of reducing the quality of the optical device.

The present invention has been made in view of the above circumstances, and a main technical object thereof is to provide a light-emitting layer on a surface layer of a single crystal substrate and to be divided by a plurality of predetermined lines formed in a lattice shape. A method in which an optical device wafer in which a light device is formed in a plurality of regions is divided into a single optical device along a predetermined dividing line, and the optical device wafer is not degraded in quality.

In order to solve the above-mentioned main technical problems, the optical device wafer processing method according to the present invention is characterized in that a light-emitting layer is formed on a surface layer of a single crystal substrate, and is divided by a plurality of predetermined dividing lines formed in a lattice shape. A method of processing an optical device wafer in which a plurality of optical devices are formed in a plurality of regions and is divided into a plurality of optical devices along a predetermined dividing line. The method for processing the optical device wafer includes: an opening number setting step of dividing the number of openings (NA) of the collecting lens for collecting the pulsed laser light by the refractive index (N) of the single crystal substrate by 0.05~ The range of 0.2 sets the number of openings (NA) of the condensing lens; the luminescent layer removing step is performed by locating the condensed spot of the pulsed laser light from the back side of the single crystal substrate to the vicinity of the luminescent layer and irradiating along the dividing line. Removing the luminescent layer along a predetermined dividing line; a latent shield type through hole forming step from the step of removing the luminescent layer The back side of the single crystal substrate of the optical device wafer positions the condensed spot of the pulsed laser light near the surface of the single crystal substrate and irradiates along the predetermined dividing line to extend from the surface of the single crystal substrate to the back surface to make the pores and The amorphous growth of the pores is prevented to form a shield-type through-hole; and the dividing step is performed by applying an external force to the optical device wafer on which the shield-type through-hole forming step is performed to divide the optical device into individual optical devices.

The luminescent layer removing step irradiates the pulsed laser light with a smaller energy than the energy of the pulsed laser beam forming the shield-type through hole in the latent shield type through hole forming step and overlapping the condensed spots.

In the above-mentioned luminescent layer removing step, the irradiated pulsed laser light is set to have an energy per pulse of 2 μJ to 6 μJ, and the irradiated pulsed laser light is set to be every 1 pulse in the above-described shield-type through-hole forming step. The energy is 30 μJ or more.

In the method of processing a wafer according to the present invention, the number of openings (NA) of the collecting lens for collecting the pulsed laser light is divided by the value of the refractive index (N) of the single crystal substrate to be 0.05 to 0.2. The number of openings (NA) of the optical lens is removed by dividing the condensed spot of the pulsed laser light from the back side of the single crystal substrate to the vicinity of the luminescent layer and irradiating along the dividing line. After the luminescent layer removing step of the luminescent layer, the condensing point of the pulsed laser ray is positioned near the surface of the single crystal substrate from the back side of the single crystal substrate of the optical device wafer, and is irradiated along the dividing line to The surface of the crystal substrate extends to the back surface to form pores and a latent shield type through hole forming step of preventing the amorphous growth of the pores from forming a latent shield type through hole.

Therefore, since the light-emitting layer laminated on the dividing line of the surface of the single crystal substrate is removed along the dividing line at the time of performing the shield-type through hole forming step, there is no optical device adjacent to the dividing line. The situation in which the luminescent layer causes damage. Further, since the pulsed laser beam is irradiated to form a shield-type through hole by growing the pores and preventing the amorphous growth of the pores between the light collecting point positioned on the single crystal substrate and the incident side of the pulsed laser light, Even a single crystal substrate having a thickness of, for example, 300 μm can be formed by continuously extending from the laser irradiation surface (upper surface) to the lower surface to form a shield-type through hole, and therefore, even if the thickness of the single crystal substrate is thick, it can be irradiated only once. Pulsed laser light, so productivity is very good. Further, since the debris does not scatter during the latent shield type through hole forming step, the problem of lowering the quality of the device can be solved.

2‧‧‧Optical device wafer

20‧‧‧Sapphire substrate

20a, 21a‧‧‧ surface

20b‧‧‧back

21‧‧‧Lighting layer

211‧‧‧Removing the ditch

22‧‧‧Division line

23‧‧‧Light devices

24‧‧‧Spot shield through hole

241‧‧‧Pore

242‧‧‧Amorphous

3‧‧‧Ring frame

30‧‧‧Cut Tape

4‧‧‧ Laser processing equipment

41‧‧‧ collet table for laser processing equipment

42‧‧‧Laser light irradiation mechanism

421‧‧‧ casing

422‧‧‧ concentrator

422a‧‧‧ Condenser lens

43‧‧‧ camera organization

6‧‧‧Segmentation device

61‧‧‧Frame keeping mechanism

611‧‧‧Frame holding members

611a‧‧‧Loading surface

612‧‧‧ fixture

62‧‧‧ tape expansion mechanism

621‧‧‧Expansion roller

622‧‧‧Support flange

623‧‧‧Support institutions

623a‧‧‧ cylinder

623b‧‧‧ piston rod

63‧‧‧ pick-up chuck

LB‧‧‧Laser light

S‧‧‧ interval

P‧‧‧ spotlight

X, X1, Y‧‧‧ arrow symbol

、, θ‧‧‧ angle

1(a)-(b) are perspective views of a wafer of an optical device processed as a wafer processed by the method for processing a wafer of the present invention, and a cross-sectional view showing an enlarged main portion; FIG. 2 is a view showing FIG. FIG. 3 is a perspective view showing a state in which a light-emitting device wafer is adhered to a dicing tape provided on an annular frame; FIG. 3 is a luminescent layer removing step and a shield-type through-hole in a method for processing a wafer according to the present invention; FIG. 4(a)-(c) are explanatory views of the luminescent layer removing step of the wafer processing method according to the present invention; FIGS. 5(a)-(e) are diagrams of main parts of the laser processing apparatus forming the steps; Description of the latent shield type through hole forming step of the wafer processing method according to the present invention; FIG. 6 is a view showing the aperture number (NA) of the condensing lens and the refractive index (N) and the number of openings (NA) of the optical device wafer. Divided by the relationship of the value of the refractive index (N) (S=NA/N); FIG. 7 is a view showing the state in which the sapphire substrate (Al ₂ O ₃ ) and the tantalum carbide (SiC) substrate have been formed into the through-hole type. a diagram of the energy of the pulsed laser light and the length of the shield-type through-hole; FIG. 8 is a processing method for implementing the wafer according to the present invention; FIG perspective division step of dividing means; and FIG. 9 (a) - (c) is a diagram illustrating a wafer processing method according to the present invention, the dividing step;

Form for implementing the invention

Hereinafter, the method of processing the wafer of the present invention will be described in more detail with reference to the additional drawings.

Fig. 1 (a) and (b) are a perspective view showing an optical device wafer divided into individual optical devices by the method for processing a wafer of the present invention, and a cross-sectional view showing an enlarged main portion. The optical device wafer 2 shown in FIGS. 1(a) and 1(b) is a light-emitting layer (epitaxial layer) made of a nitride semiconductor laminated on the surface 20a of a sapphire substrate 20 having a thickness of 300 μm as a single crystal substrate. )twenty one. Further, the light-emitting layer (epitaxial layer) 21 is divided into a plurality of predetermined dividing lines 22 which are formed in a lattice shape, and an optical device 23 such as a light-emitting diode or a laser diode is formed in such a plurality of divided regions. .

In order to divide the above-mentioned optical device wafer 2 along the dividing line 22, first, a wafer supporting step is performed to adhere the optical device wafer 2 to the mounting. The surface of the dicing tape on the annular frame. In other words, as shown in FIG. 2, the surface 21a of the light-emitting layer (epitaxial layer) 21 of the optical device wafer 2 is adhered to the dicing tape 30 of the upper peripheral portion so as to cover the inner opening portion of the annular frame 3. surface. Therefore, the optical device wafer 2 adhered to the surface of the dicing tape 30 becomes exposed to the back surface 20b of the sapphire substrate 20.

Fig. 3 shows a laser processing apparatus that performs laser processing along the dividing line 22 of the optical device wafer 2 on which the wafer supporting step has been carried out. The laser processing apparatus 4 shown in FIG. 3 includes a collet table 41 for holding a workpiece, a laser beam irradiation mechanism 42 for irradiating a laser beam to the workpiece held on the chuck table 41, and a photographing chuck. The image pickup mechanism 43 of the workpiece held on the table 41. The chuck table 41 is configured to be capable of attracting and holding the workpiece, and is formed to be movable in the processing conveyance direction indicated by the arrow symbol X in FIG. 3 by a processing conveyance mechanism not shown, and can be illustrated by An indexing mechanism, not shown, is made movable in the indexing direction indicated by the arrow symbol Y in Fig. 3.

The above-described laser beam irradiation mechanism 42 includes a cylindrical sleeve 421 that is substantially horizontal. A pulsed laser light emitting mechanism having a pulsed laser light emitter and a repetition frequency setting mechanism, not shown, is disposed in the sleeve 421. A concentrator 422 is provided at the front end portion of the sleeve 421, and is provided with a condensing lens 422a for collecting pulsed laser light emitted from the pulsed laser beam emitting means. The condensing lens 422a of the concentrator 422 sets the number of openings (NA) as follows. In other words, the number of openings (NA) of the condensing lens 422a is set such that the number of openings (NA) divided by the refractive index (N) of the single crystal substrate is in the range of 0.05 to 0.2 (the number of openings setting step). Furthermore, laser light exposure The mechanism 42 is provided with a condensed spot position adjusting mechanism (not shown) for adjusting the position of the condensed spot of the pulsed laser beam condensed by the condensing lens 422a of the concentrator 422.

The imaging unit 43 installed at the distal end portion of the sleeve 421 constituting the laser beam irradiation unit 42 may be an infrared ray for irradiating the workpiece with infrared rays in addition to a normal imaging element (CCD) that images the visible light. An illuminating mechanism, an optical system that captures infrared rays irradiated by the infrared illuminating means, and an imaging element (infrared CCD) that can output an electrical signal corresponding to the infrared ray captured by the optical system, and the captured image signal Transfer to the control unit not shown.

When the laser processing apparatus 4 is used to perform laser processing along the dividing line 22 of the optical device wafer 2 on which the wafer supporting step is performed, first, the dicing tape 30 to which the optical device wafer 2 is pasted is used. The side is placed on the chuck table 41 of the laser processing apparatus 4 shown in Fig. 3 described above. Further, the optical device wafer 2 is held on the chuck table 41 by the protective tape 30 by a suction mechanism not shown in the drawing (wafer holding step). Therefore, the optical device wafer 2 held on the chuck table 41 becomes the upper side of the back surface 20b of the sapphire substrate 20. Further, in FIG. 3, the annular frame 3 on which the dicing tape 30 is attached is omitted, and the annular frame 3 is held by a suitable frame holding mechanism disposed on the cradle 41. In this way, the chuck table 41 that sucks and holds the optical device wafer 2 can be positioned directly below the imaging mechanism 43 through a processing transfer mechanism not shown.

When the chuck table 41 is positioned directly below the camera mechanism 43, a calibration operation can be performed to utilize the camera mechanism 43 and a control device not shown. The processing area of the optical device wafer 2 that should be laser processed is detected. That is, the imaging unit 43 and the control unit (not shown) perform a division line 22 for forming the first line in the optical device wafer 2, and a laser beam for irradiating the laser beam along the division line 22 The position of the concentrator 422 of the light irradiation mechanism 42 is aligned with the image processing such as pattern matching to complete the calibration of the laser light irradiation position (calibration step). Further, the alignment of the laser beam irradiation position is similarly performed on the division planned line 22 formed in the second direction orthogonal to the first direction on the optical device wafer 2. At this time, although the surface 21a of the light-emitting layer (epitaxial layer) 21 on which the optical device wafer 2 is formed with the division planned line 22 is located on the lower side, since the image pickup mechanism 43 has the above-described optical illumination mechanism and the infrared ray-capable optical Since the system and the imaging means (infrared CCD) that can output an electric signal corresponding to infrared rays can be penetrated from the back surface 20b of the sapphire substrate 20 as a single crystal substrate, the planned dividing line 22 can be imaged.

After the above-described calibration step, the condensed spot of the pulsed laser light is positioned near the luminescent layer 21 from the side of the back surface 20b of the sapphire substrate 20 constituting the single crystal substrate of the optical device wafer 2 to be along the dividing line. When the irradiation is performed 22, the luminescent layer removing step of removing the luminescent layer 21 along the dividing line 22 can be performed. That is, as shown in FIG. 4(a), the chuck stage 41 is moved to the laser beam irradiation area where the concentrator 422 of the laser beam irradiation mechanism 42 that irradiates the laser beam is irradiated, and the predetermined division is scheduled. Line 22 is positioned directly below concentrator 422. At this time, the optical device wafer 2 shown in FIG. 4(a) is positioned such that one end (the left end of FIG. 4(a)) of the division planned line 22 is located directly below the concentrator 422. And, the convergence point position adjustment mechanism not shown in the actuation diagram is along The concentrator 422 is moved in the optical axis direction, and the condensed spot P of the pulsed laser beam LB is positioned from the side of the back surface 20b of the sapphire substrate 20 constituting the single crystal substrate of the optical device wafer 2 to the surface 20a side of the sapphire substrate 20. (The vicinity of the light-emitting layer (epitaxial layer) 21 side) (converging point positioning step).

After the concentrating point positioning step is performed as described above, the luminescent layer removing step may be performed to activate the laser beam illuminating unit 42 to illuminate the pulsed laser beam LB from the concentrator 422. That is, while the pulsed laser beam LB having a wavelength that is transparent to the sapphire substrate constituting the single crystal substrate of the optical device wafer 2 is irradiated from the concentrator 422, the chuck table 41 is placed in FIG. 4(a). The direction indicated by the arrow symbol X1 is moved at a predetermined conveying speed (light emitting layer removing step). Further, as shown in FIG. 4(b), when the irradiation position of the concentrator 422 of the laser beam irradiation means 42 reaches the other end of the division planned line 22 (the right end of FIG. 4(b)), the pulse laser is stopped. The irradiation of the light simultaneously stops the movement of the chuck table 41.

The processing conditions in the above-described luminescent layer removing step can be exemplified as follows.

Wavelength: 1030nm

Repeat frequency: 50kHz

Energy per pulse: 2μJ~6μJ

Converging point diameter: φ 10μm

Processing transfer speed: 250mm / sec

By performing the luminescent layer removing step under the above processing conditions, the overlap ratio of the spot diameter of the pulsed laser light can be made 50%, and as shown in FIG. 4(c), the sapphire as a single crystal substrate can be used. Surface of substrate 20 The light-emitting layer 21 on the laminated division line 22 is continuously broken along the division planned line 22 to form the removal groove 211.

As described above, if the above-described light-emitting layer removing step is to be performed along the predetermined dividing line 22, the chuck table 41 can be indexed only in the direction indicated by the arrow symbol Y by the division formed on the optical device wafer 2. The interval of the line 22 (indexing step) is predetermined to complete the above-described luminescent layer removing step. By performing the above-described light-emitting layer removing step for all the division planned lines 22 formed in the predetermined direction, the chuck stage 41 can be rotated by 90 degrees to be divided along the division formed in the first direction. The predetermined line 22 is a dividing line 22 extending in the second direction orthogonal to the light-emitting layer removing step.

Further, in the pulsed laser beam to be irradiated in the above-described luminescent layer removing step, the energy per pulse is preferably set to 2 μJ to 6 μJ. The energy per pulse of the pulsed laser beam irradiated in this luminescent layer removing step will be described in detail later.

After the luminescent layer removing step is performed as described above, the latent shield type via forming step can be performed to position the condensed spot of the pulsed laser light from the back side of the sapphire substrate 20 constituting the single crystal substrate of the optical device wafer 2. Irradiation along the dividing line 22 in the vicinity of the surface of the sapphire substrate 20 as a single crystal substrate extends from the surface of the sapphire substrate 20 as a single crystal substrate to the back surface to grow pores and prevent the amorphous growth of the pores. Form a shield-type through hole. To perform the shield-type through-hole forming step, the chuck stage 41 holding the optical device wafer 2 on which the above-described light-emitting layer removing step is carried is moved as shown in FIG. 5(a) to the laser beam irradiated with the laser beam. The laser beam illuminating area where the concentrator 422 of the light illuminating mechanism 42 is located, and the predetermined division is scheduled Line 22 is positioned directly below concentrator 422. At this time, the optical device wafer 2 shown in FIG. 5(a) is positioned such that one end of the division planned line 22 (the left end of FIG. 5(a)) is located immediately below the concentrator 422. Further, the condensing point position adjusting mechanism not shown in the drawing moves the concentrator 422 in the optical axis direction, and applies pulsed laser light from the back surface 20b side of the sapphire substrate 20 which constitutes the single crystal substrate of the optical device wafer 2. The condensed spot P of the LB is positioned near the surface 20a of the sapphire substrate 20 (converging point positioning step).

After the concentrating point positioning step is performed as described above, the latent shield type through hole forming step may be implemented to actuate the laser beam illuminating mechanism 42 to illuminate the pulsed laser beam LB from the concentrator 422 and to position the crystal device from the illuminating device. The condensed spot P in the vicinity of the surface 20a of the sapphire substrate 20 as the single crystal substrate of the circle 2 is incident on the pulsed laser ray incident side (the back surface 20b side of the sapphire substrate 20) to form pores and amorphous which protects the pores. Form a shield-type through hole. That is, while the pulsed laser beam LB having a wavelength that is transparent to the sapphire substrate constituting the single crystal substrate of the optical device wafer 2 is irradiated from the concentrator 422, the chuck table 41 is placed in FIG. 5(a). The direction indicated by the arrow symbol X1 is moved at a predetermined conveying speed (a shield-type through hole forming step). Further, as shown in FIG. 5(b), when the irradiation position of the concentrator 422 of the laser beam irradiation means 42 reaches the other end of the division planned line 22 (the right end of FIG. 5(b)), the pulse laser is stopped. The irradiation of the light simultaneously stops the movement of the chuck table 41.

The processing conditions of the above-described latent shield type through hole forming step can be exemplified as follows.

Wavelength: 1030nm

Repeat frequency: 50kHz

Energy per pulse: 30μJ or more

Converging point diameter: φ 10μm

Processing transfer speed: 500mm / sec

By performing the above-described shield-type through-hole forming step, inside the sapphire substrate 20 constituting the single-crystal substrate of the optical device wafer 2, the pulsed laser beam LB is positioned as shown in FIG. 5(c). The surface 20a side of the single crystal substrate 20 of the condensed point P continuously extends to the back surface 20b of the single crystal substrate 20 as an irradiation surface, and the pores 241 and the amorphous 242 formed around the pores 241 are grown and divided along the division. The line 22 forms an amorphous shield-type through hole 24 at a predetermined interval (in the present embodiment, an interval of 10 μm (processing transfer speed: 500 mm/sec) / (repetition frequency: 50 kHz). The shield-type through hole 24 As shown in FIGS. 5(d) and 5(e), the pores 241 having a diameter of about 1 μm formed at the center and the amorphous 242 having a diameter of φ 10 μm formed around the pores 241 are formed. In the present embodiment, the adjacent amorphous 242 is formed to be in contact with each other. Further, the amorphous shield type through hole 24 formed in the latent shield type through hole forming step is It extends from the side of the surface 20a of the sapphire substrate 20 which constitutes the single crystal substrate of the optical device wafer 2 to Since the back surface 20b of the sapphire substrate 20 of the surface is grown and formed, even if the thickness of the wafer is thick, only the pulsed laser light can be irradiated once, and the productivity is relatively good. Thus, even the optical device wafer 2 When the thickness is, for example, 300 μm, the shield-type through hole 24 is formed from the surface 20a side of the sapphire substrate 20 to the back surface 20b as the irradiation surface, so that it does not occur on the optical device wafer 2. The case of warping. Also, since there is no debris scattering in the latent shield type through hole forming step, it is also possible Solve the problem of reducing the quality of the device. Further, since the light-emitting layer 21 laminated on the dividing line 22 of the surface of the sapphire substrate 20 as a single crystal substrate as described above can be removed along the dividing line 22 at the time of performing the shield-type through-hole forming step Therefore, there is no possibility of damage to the light-emitting layer of the optical device 23 adjacent to the division planned line 22.

As described above, after the above-described shield-type through-hole forming step is performed along the predetermined dividing line 22, the chuck table 41 is only indexed and moved on the optical device wafer 2 in the direction indicated by the arrow symbol Y. The interval of the division planned line 22 (indexing step) is formed to continue the above-described shield type through hole forming step. In this way, after the above-described shield-type through-hole forming step is performed on all the divided planned lines 22 formed in the first direction, the chuck stage 41 can be rotated by 90 degrees and along with respect to the first direction. The division planned line 22 formed above is a step of forming the above-described shield type through hole by dividing the predetermined line 22 extending in the second direction orthogonal to the orthogonal direction.

In the above-described shield type through hole forming step, a good shield type through hole 24 is formed, and the number of openings (NA) of the collecting lens 422a is set as the number of openings (NA) divided by the single crystal substrate as described above. The value of the refractive index (N) (S = NA / N) is important in the range of 0.05 to 0.2.

Here, the relationship between the number of openings (NA) and the refractive index (N) and the number of openings (NA) divided by the value of the refractive index (N) (S=NA/N) will be described with reference to FIG. 6. In FIG. 6, the pulsed laser beam LB incident on the condensing lens 422a is condensed by forming an angle (θ) with respect to the optical axis of the condensing lens 422a. At this time, sin θ is the number of openings (NA) of the condensing lens 422a (NA = sin θ). Irradiating the pulsed laser beam LB condensed by the collecting lens 422a to the optical device wafer formed of the single crystal substrate At 2 o'clock, since the single crystal substrate constituting the optical device wafer 2 has a higher density than air, the pulsed laser beam LB is refracted from the angle (θ) to an angle (α) and condensed into a condensed point P. At this time, the angle (α) with respect to the optical axis differs depending on the refractive index (N) of the single crystal substrate constituting the optical device wafer 2. Since the refractive index (N) is (N = sin θ / sin α), the number of openings (NA) divided by the value of the refractive index (N) of the single crystal substrate (S = NA / N) becomes sin α. Therefore, it is important to set sin α in the range of 0.05 to 0.2 (0.05 ≦ sin α ≦ 0.2).

Hereinafter, the reason why the number of openings (NA) of the condensing lens 422a is divided by the value (S=NA/N) of the refractive index (N) of the single crystal substrate is set in the range of 0.05 to 0.2 will be described.

[Experiment 1-1]

A sapphire (Al ₂ O ₃ ) substrate (refractive index: 1.7) having a thickness of 1000 μm was formed into a latent shield type through hole under the following processing conditions, and the good shape of the through shield type through hole was determined.

Processing conditions

Wavelength: 1030nm

Repeat frequency: 50kHz

Pulse width: 10ps

Average output: 3W

Converging point diameter: φ 10μm

Processing transfer speed: 500mm / sec

As described above, in the sapphire substrate (refractive index: 1.7), the number of openings (NA) of the condensing lens 422a is divided by the value (S=NA/N) of the refractive index (N) of the single crystal substrate. A range of 0.05 to 0.2 to form a shield-type through hole. Therefore, in the sapphire substrate (refractive index: 1.7), it is important to set the number of apertures (NA) of the condensing lens 422a that collects the pulsed laser light to 0.1 to 0.35.

[Experiment 1-2]

A ruthenium carbide (SiC) substrate (refractive index: 2.63) having a thickness of 1000 μm was formed into a shield-type through-hole by the following processing conditions, and the good shadow of the shield-type through-hole was determined.

Processing conditions

Wavelength: 1030nm

Repeat frequency: 50kHz

Pulse width: 10ps

Average output: 3W

Converging point diameter: φ 10μm

Processing transfer speed: 500mm / sec

As described above, in the tantalum carbide (SiC) substrate (refractive index: 2.63), the number of openings (NA) of the collecting lens 422a for collecting the pulsed laser light is divided by the refractive index (N) of the single crystal substrate. The value (S=NA/N) is set in the range of 0.05 to 0.2 to form a shield-type through hole. Therefore, in the tantalum carbide (SiC) substrate, it is important to set the number of apertures (NA) of the collecting lens 422a that collects the pulsed laser light to 0.15 to 0.55.

Furthermore, since the shield-type through-hole is formed from the condensed spot P to the side that illuminates the laser beam, the condensed spot of the pulsed laser ray must be positioned on the opposite side to the side from which the pulsed laser beam is incident. The inner side of the face is adjacent.

It can be confirmed from the above experiment 1-1 and experiment 1-2 that it can be The number of openings (NA) of the condensing lens 422a that collects the pulsed laser light is divided by the value of the refractive index (N) of the single crystal substrate (S=NA/N) in the range of 0.05 to 0.2 to form a shield-type pass. hole.

Next, the correlation between the energy of the pulsed laser light and the length of the through-hole type of the through hole is examined.

[Experiment 2]

The pulsed laser light is irradiated onto a sapphire (Al ₂ O ₃ ) substrate or a tantalum carbide (SiC) substrate having a thickness of 1000 μm under the following processing conditions, and the energy of the pulsed laser light (μJ/1 pulse) and the shield are obtained. The relationship between the length (μm) of the through hole.

Processing conditions

Wavelength: 1030nm

Repeat frequency: 50kHz

Pulse width: 10ps

Converging point diameter: φ 10μm

Processing transfer speed: 500mm / sec

The average output was set to increase the average output at intervals of 0.05 W (1 μJ/1 pulse) until the shield-type through-holes were formed, and the average output was made at intervals of 0.5 W (10 μJ/1 pulse) after forming the shield-type through-holes. The length (μm) of the through-hole type through hole is measured until it rises to 10 W (200 μJ/1 pulse).

It can be seen that the sapphire (Al ₂ O ₃ ) substrate and the tantalum carbide (SiC) substrate have the energy of the pulsed laser light (μJ/1 pulse) and the shield-type through-hole in the state in which the shield-type through hole is formed. The length (μm) is represented by the graph shown in Figure 7, and the energy of the pulsed laser light is 5 μJ/1 pulse or more, and the length of the shield-type through-hole is made Y (μm), and the pulse laser is applied. When the energy of the light is X (μJ/1 pulse), there is a correlation of Y = (3.0 - 4.0 μm / μJ) X + 50 μm. Therefore, in the case of a sapphire (Al ₂ O ₃ ) substrate having a thickness of 500 μm, the energy of the pulsed laser beam having the length of the shield-type through hole set to the thickness of the single crystal substrate becomes 160 μJ/1 pulse or more.

Next, the wavelength of the pulsed laser light and the formation of the through-hole type through hole are reviewed.

[Experiment 3-1]

The sapphire substrate having a thickness of 1000 μm was examined under the following processing conditions and the wavelength of the pulsed laser light was lowered at 2940 nm, 1550 nm, 1030 nm, 515 nm, 343 nm, 257 nm, and 151 nm to verify whether the band gap was 8.0 eV ( A shield-type through hole is formed in the sapphire substrate of the converted wavelength: 155 nm.

Processing conditions

Repeat frequency: 50kHz

Pulse width: 10ps

Average output: 3W

Converging point diameter: φ 10μm

Processing transfer speed: 500mm / sec

It can be confirmed that, as described above, when the wavelength of the pulsed laser light is set to be twice or more the wavelength (converted wavelength: 155 nm) corresponding to the band gap of 8.0 eV in the sapphire substrate, the shield type can be formed. hole.

[Experiment 3-2]

A 1000 μm thick tantalum carbide (SiC) substrate was tested under the following processing conditions and the wavelength of the pulsed laser light was lowered at 2940 nm, 1550 nm, 1030 nm, 515 nm, and 257 nm to verify whether the band gap could be 2.9 eV ( A shield-type through hole is formed in a tantalum carbide (SiC) substrate of a converted wavelength: 425 nm.

Processing conditions

Repeat frequency: 50kHz

Pulse width: 10ps

Average output: 3W

Converging point diameter: φ 10μm

Processing transfer speed: 500mm / sec

It can be confirmed that, as described above, when the wavelength of the pulsed laser light is set to be twice or more the wavelength (converted wavelength: 425 nm) corresponding to an energy band gap of 2.9 eV in the tantalum carbide (SiC) substrate, a latent potential can be formed. Shield through hole.

It can be confirmed from Experiments 3-1 and 3-2 described above that when the wavelength of the pulsed laser light is set to be twice or more the wavelength of the band gap of the single crystal substrate, the shield type through hole can be formed. .

Next, the energy per pulse of the pulsed laser beam irradiated in the above-described luminescent layer removing step will be described.

When the energy of the pulsed laser light per pulse is 10 μJ or more, it can be seen from the results of the above experiment 2 that although the shield-type through hole can be formed, the optical device wafer is divided into individual light devices, and the shield type is formed. When the length of the through hole must be 150 μm or more, the energy per pulse becomes 30 μJ or more.

However, in a state where the light-emitting layer removing step is not performed, pulsed laser light having an energy of 30 μJ or more per pulse is collected from the back surface 20b side of the sapphire substrate 20 as a single crystal substrate of the optical device wafer 2. When the dot is positioned near the surface 20a and irradiated along the dividing line 22, the light-emitting layer 21 laminated on the dividing line 22 of the surface 20a of the sapphire substrate 20 and the light-emitting layer of the optical device 23 adjacent to the dividing line 22 are The quality of the optical device 23 is degraded by the destruction of the chain.

Then, the inventors of the present invention presume that by performing the above-described light-emitting layer removing step before the implementation of the above-described shield-type through-hole forming step, only the light-emitting layer on the dividing line 22 can be removed, thereby preventing the formation of the shield type. At the time of the through hole, the luminescent layer of the optical device 23 is subjected to a chain destruction, and is performed. An experiment for removing only the light-emitting layer on the dividing line 22 was performed.

[Experiment 4-1]

A pulsed laser beam having an energy of 10 μJ and 20 μJ per pulse of the through-hole type can be formed from the back surface 20b side of the sapphire substrate 20 of the optical device wafer 2 as a single crystal substrate When the vicinity of the surface 20a is irradiated along the division planned line 22, the light-emitting layer on the division planned line 22 cannot be broken. This is considered to be because the energy of the pulsed laser light is almost always used in the formation of the shield-type through hole.

[Experiment 4-2]

A pulsed laser beam having an energy of 1 μJ to 9 μJ per one pulse of the through-hole type cannot be formed from the back surface 20b side of the sapphire substrate 20 of the optical device wafer 2 as a single crystal substrate When the surface 20a is irradiated along the dividing line 22, when the energy per pulse is in the range of 2 μJ to 6 μJ, only the light-emitting layer on the dividing line 22 can be broken.

Further, when the energy per pulse is 7 μJ to 9 μJ, the light-emitting layer 21 on the predetermined line 22 and the light-emitting layer of the optical device 23 adjacent to the planned dividing line 22 are damaged by the chain. Therefore, it is important to set the energy per pulse of the pulsed laser beam irradiated in the step of removing the light-emitting layer to 2 μJ to 6 μJ.

When the above-described shield-type through-hole forming step has been carried out, a wafer dividing step can be performed to impart an external force to the optical device wafer 2, and a thin hole 241 and an amorphous layer formed around the fine hole 241 are continuously formed along the continuous surface. The division planned line 22 of the shield-type through hole 24 formed by 242 divides the optical device wafer 2 into individual optical devices 23. The wafer dividing step is carried out using the dividing device 6 shown in FIG. The dividing device 6 shown in FIG. 8 includes a frame holding mechanism 61 that holds the annular frame 3, and a tape expanding mechanism 62 that expands the optical device wafer 2 attached to the annular frame 3 held by the frame holding mechanism 61. And the pick-up collet 63. The frame holding mechanism 61 is composed of an annular frame holding member 611 and a plurality of jigs 612 arranged as fixing means on the outer periphery of the frame holding member 611. A mounting surface 611a on which the annular frame 3 is placed is formed on the upper surface of the frame holding member 611, and the annular frame 3 is placed on the mounting surface 611a. Further, the annular frame 3 placed on the mounting surface 611a is fixed to the frame holding portion 611 by the transmission jig 612. The frame holding mechanism 61 thus constructed is supported to advance and retreat in the vertical direction by the tape expansion mechanism 62.

The tape expansion mechanism 62 includes an expansion roller 621 disposed inside the annular frame holding member 611. This expansion roller 621 has an inner diameter and an outer diameter which are smaller than the inner diameter of the annular frame 3 and larger than the outer diameter of the optical device wafer 2 attached to the dicing tape 30 attached to the annular frame 3. Further, the expansion drum 621 is provided with a support flange 622 at the lower end. The tape expansion mechanism 62 in the present embodiment includes a support mechanism 623 that can advance and retract the annular frame holding member 611 in the vertical direction. This support mechanism 623 is constituted by a plurality of air cylinders 623a disposed on the support flange 622, and a piston rod 623b is coupled to the lower surface of the annular frame holding member 611. As described above, the support mechanism 623 composed of the plurality of cylinders 623a allows the annular frame holding member 611 to have a reference height of substantially the same height between the mounting surface 611a and the upper end of the expansion drum 621 as shown in Fig. 9(a). The position is moved in the up and down direction between the expansion position below the predetermined amount of the upper end of the expansion drum 621 as shown in Fig. 9(b).

The wafer dividing step performed by using the dividing device 6 configured as described above will be described with reference to FIG. 9. In other words, the annular frame 3 on which the dicing tape 30 attached to the optical device wafer 2 is mounted is placed on the mounting surface of the frame holding member 611 constituting the frame holding mechanism 61 as shown in Fig. 9(a). The 611a is fixed to the frame holding member 611 through the jig 612 (frame holding step). At this time, the frame holding member 611 is positioned at the reference position shown in FIG. 9(a). Next, the plurality of cylinders 623a constituting the support mechanism 623 of the tape expansion mechanism 62 are operated to lower the annular frame holding member 611 to the expanded position shown in Fig. 9(b). Therefore, since the annular frame 3 fixed to the mounting surface 611a of the frame holding member 611 is also lowered, the dicing tape 30 attached to the annular frame 3 can be brought into contact with the expansion roller as shown in Fig. 9(b). The upper end edge of 621 is expanded (tape expansion step). As a result, since the optical device wafer 2 attached to the dicing tape 30 is radially actuated by the tensile force, the predetermined dividing line 22 is formed along the continuous formation of the shield-type through hole 24 to reduce the strength thereof. The optical devices 23 are separated into one by one, and a space S is formed between the optical devices 23.

Next, as shown in FIG. 9(c), the pickup chuck 63 is actuated to suck the optical device 23, peel it from the dicing tape 30, and pick it up and transport it to a tray or a die bonding step (not shown). Further, in the pickup step, as described above, since the gap S between the one optical devices 23 attached to the dicing tape 30 is enlarged, there is no possibility of contact with the adjacent device 23, but Easily pick up.

2‧‧‧Optical device wafer

20‧‧‧Sapphire substrate

20b‧‧‧back

21‧‧‧Lighting layer

21a‧‧‧Surface

211‧‧‧Removing the ditch

22‧‧‧Division line

24‧‧‧Spot shield through hole

241‧‧‧Pore

242‧‧‧Amorphous

30‧‧‧Cut Tape

41‧‧‧ chuck table

422‧‧‧ concentrator

422a‧‧‧ Condenser lens

LB‧‧‧Laser light

P‧‧‧ spotlight

X1‧‧‧ arrow symbol

Claims (2)

A method for processing an optical device wafer is an optical device crystal in which a light-emitting layer is formed on a surface layer of a single crystal substrate, and an optical device is formed in a plurality of regions defined by a plurality of predetermined dividing lines formed in a lattice shape. A method for processing a light device wafer which is divided into a plurality of optical devices along a predetermined dividing line, characterized in that the method for processing the optical device wafer comprises: a number of openings setting step for collecting a collecting lens of a pulsed laser beam The number of openings (NA) is set by the number of openings (NA) of the condensing lens divided by the value of the refractive index (N) of the single crystal substrate of 0.05 to 0.2; the luminescent layer removing step is performed from the back side of the single crystal substrate. The condensed spot of the pulsed laser light is positioned near the luminescent layer and irradiated along the dividing line to remove the luminescent layer along the dividing line; the latent shield type through hole forming step, the optical device from which the luminescent layer removing step is performed The back side of the single crystal substrate of the wafer positions the condensed spot of the pulsed laser light near the surface of the single crystal substrate and is irradiated along the dividing line to extend from the surface of the single crystal substrate to the back surface. a fine hole and an amorphous growth preventing the pores to form a shield-type through hole; and a dividing step of applying an external force to the optical device wafer on which the shield-type through hole forming step is performed to divide the light into one light The illuminating layer removing step irradiates the pulsed laser light with a smaller energy than the energy of the pulsed laser light forming the latent shield type through hole in the latent shield type through hole forming step and overlapping the condensed spots . The method for processing an optical device wafer according to claim 1, wherein In the luminescent layer removing step, the irradiated pulsed laser light is set to have an energy per pulse of 2 μJ to 6 μJ, and the irradiated pulsed laser light is set to an energy per pulse in the latent shield type through hole forming step. 30μJ or more.